The present invention refers to a needle machine for needling non-woven fiber fleece webs, comprising at least one support for supporting a fiber fleece web to be needled, at least one movable needle bar equipped with a plurality of needles, said needle bar being put into an oscillating movement, and comprising a drive for the needle bar, containing a first drive means connected to the needle bar and providing the needle bar with a movement component (vertical component) extending perpendicularly to the support, a second drive means connected to the needle bar and providing the needle bar with a movement component (horizontal component) extending in parallel to the support, and a means for changing the movement stroke of the horizontal component. Such a machine is known from U.S. Pat. No. 5,732,453 to Dilo et al., the disclosure of which being incorporated by reference into this description.
When needling a fiber fleece web in a needle machine, in which the needle bar performs a movement that is only directed perpendicularly to the fiber fleece web to be needled, the fiber fleece web continuously transported through the needle machine by supply and take-up rollers mounted in a frame of the needle machine is braked by the needles during the period within which the needles are stitched into the fiber fleece. This leads to the fiber fleece being deformed and the needles being resiliently bent in cyclically recurring cycles. These effects are disadvantageous for the fiber fleece and the needle machine. This could be prevented in that at a given stroke frequency of the needle bar, the transport speed of the fiber fleece web through the needle machine was reduced. This, however reduced productivity. In particular in when manufacturing machine felts that have great lengths and widths, a great transport speed is required for an economic manufacture. Deformation of the fiber fleece may result in an irregularity of the fiber fleece surface, which later becomes visible in the paper that is manufactured by the aid of this fleece or felt.
To avoid these disadvantageous effects, a second drive is associated to the needle bar according to the above-mentioned U.S. Pat. No. 5,732,453, said second drive setting the needle bar cyclically and synchronously to said first drive in a motion (horizontal motion) oscillating parallel to the fiber fleece web with its stitching direction (vertical direction) extending perpendicular to the fiber fleece. The horizontal movement extends in and opposite to the transport direction of the fiber fleece web through the needle machine and is superimposed in time by the perpendicular stitching-in movement of the needle bar such that the movement of the needle bar in the horizontal direction in the time section of each motion cycle in which the needles are stitched into the fiber fleece follows the movement of the fiber fleece through the needle machine caused by the supply and take-up rollers, whereas in the condition of the needles released from the fiber fleece, the return of the needle bar takes place in the horizontal direction, i.e. in parallel to the fiber fleece web into the starting position. Thus, the needle bar, seen from the side transversely to the transport direction of the fiber fleece web, performs a circulating movement, which according to the relation of the strokes of the horizontal and vertical movements is more or less circular or elliptical.
Frequently, the desire arises to change the stroke of the horizontal movement of the needle bar in a needle machine equipped in that manner, e.g. to adapt said stroke to the transport speed of the fiber fleece through the needle machine. The above-mentioned U.S. Pat. No. 5,732,453 provides a solution for this purpose in which the eccentricity of a rotating eccentric by means of which the horizontal motion component of the needle bar is caused, can be changed. The means provided for that purpose are rotatable bushings and associated coupling means. This solution is mechanically quite difficult and enables adjustments only by means of time-consuming works and only between a few positions and moreover only during standstill of the machine.